In many power generating systems it may be advantageous from the viewpoints of various design and constructional aspects to connect a generator to a prime mover, e.g. a wind turbine, via a gear-box arranged to convert the rotational speed of the prime mover into a speed range suitable for the generator. Correspondingly, in many motor applications it may be advantageous to connect an electrical motor to an actuator via a gear-box arranged to convert the rotational speed of the electrical motor into a speed range suitable for the actuator. The gear-box may comprise one or more series connected gear stages with the aid of which a desired gear-ratio is achieved. Each single gear stage can be, for example, a planet-gear stage or a cylindrical gear stage.
Challenging design aspects related to a combination of a gear-box and an electrical machine that can be a generator and/or a motor are, among others, the size and weight of the combination. Furthermore, equipment needed for lubricating, cooling, and monitoring the combination of the gear-box and the electrical machine may be complex compared with that of e.g. a gearless system. The reliability of e.g. the lubricating systems may require special attention because, as self-evident, both the lubricating system of the gear-box and the lubricating system of the electrical machine have to simultaneously work properly in order that the combination works properly. Therefore, for obtaining a sufficient effective or combined reliability, the reliabilities of the lubricating systems of the gear-box and of the electrical machine respectively have to be significantly higher than the reliability that would be required for a single lubricating system of a gearless system. However the gear-box, especially in many wind power applications, makes it possible to use an electrical machine that is significantly smaller in dimensions and weight than an electrical machine of a corresponding gearless system. Therefore, the choice whether to use a gear-box or to have a gearless system depends on many different aspects many of which are more or less in trade-off with each other. The gear-box provides many advantages and thus there is a need to provide technical solutions for alleviating or even eliminating the drawbacks related to the use of the gear-box.
Publication US2010052442 discloses a generator system that comprises a generator, a gear train, and a clutch, wherein the clutch is exposed to the gear train. The structure is integrated so that a wall of the housing of the gear train and the clutch constitutes also a wall of the housing of the generator, and in an aperture of this wall there is a lead-through sealing member around the shaft between the gear train and the generator. Thus, the construction is more compact than that of a system comprising separate generator and gear-box which are interconnected with e.g. flanges of their shafts. For example, there is a need for only one lead-through sealing member between the gear train and the generator instead of one in the generator and other in the gear-box.